Helium isotopes as geochemical indicators of a serpentinized fore‐arc mantle wedge
Bibliographic record
Abstract
New helium isotope data from hot springs on eastern Kyushu Island were obtained in order to elucidate the geographic distribution of 3He/4He ratios in the fore‐arc regions of southwest Japan. Systematic, regional variations in 3He/4He ratios are clearly distinguished across the fore arc from Kyushu Island (0.093–0.79 RA, where RA denotes the atmospheric 3He/4He ratio of 1.4 × 10−6), to Shikoku Island (0.17–3.6 RA) and to the Kii Peninsula (0.24–7.4 RA). The distribution of mantle helium relative to total helium reveals a close association with the geophysical evidence of a serpentinized fore‐arc mantle wedge including the occurrence of deep, nonvolcanic, low‐frequency tremors (LFTs), believed to be caused by upwardly mobile aqueous fluids derived from slab dehydration. Flux of mantle helium carried by aqueous fluids via a non serpentinized fore‐arc mantle wedge is very low on Kyushu Island where LFTs have not been detected and 3He/4He ratios are lower than the atmospheric ratio. On the other hand, hot springs above the regions where LFTs occur in the Kii Peninsula and northern Shikoku Island have high 3He/4He ratios, indicating a significant contribution of mantle helium carried by aqueous fluids via a serpentinized fore‐arc mantle wedge. The helium isotopes in hot and natural spring gases may be a useful geochemical indicator of a serpentinized fore‐arc mantle wedge, especially in areas with sparse seismic station coverage.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".